As you're finding out,. there's not much out there in the way of a ready-made Bible study for these books. You might have to make them up yourself, and style it upon the model of studies your group is used to doing (8--12 weeks).
It's going to be kind of tough because the two books together are kind of long. Also, they are the same basic story told from two different perspectives and they also overlap somewhat as far as the period of time they cover.
What you'll probably have to end up doing is taking a summary account of the main flow of the story, such as found here:
and use that as sort of the framework. You can then take the key events and theological concepts of the books and plug them into the storyline.I'm sure you can get 10--12 major segments that you can concentrate on each week. You don't want to study the entire books verse by verse anyway because, frankly, there's a lot of historical detail in these books (like there is in Kings and Chronicles) that can be too arcane to be studied in a group.
For reference resources, if you can get them, I'd recommend The Catholic Study Bible
, the Navarre Bible, the Holman Historical Bible Atlas
, and Introduction to Scripture
(by Scott Hahn).
Good luck. Someone in my Bible Study group has asked me to consider leading a study on the deuterocanonicals when we finish our current study in October, so I'm in the same boat as you.